Log merchandisers process tree-length logs into shorter lengths for further processing. It is desirable to process the logs as quickly as possible, with as little wasted wood as possible.
One prior art log merchandiser is disclosed in U.S. Pat. No. 6,305,259, issued to Whitworth. Whitworth discloses a log processing system whereby logs are transported via a series of conveyor belts, through a singulator and scanner, and into a cradle assembly that holds the logs while pivoting adjustable saws cut them. The saws and the log cradles are both mounted on saw boxes. The entire saw box moves laterally on wheel assemblies on floor-mounted guide rails. Each saw box, along with its associated saw and log cradle, is positioned along the length of the log prior to placing the log in the log cradle.
Hydraulic cylinders move the saw boxes to their proper positions, as determined by digital probes. Accordingly, the length of the hydraulic cylinders determines the travel distance of the saw assemblies. No saw can travel farther than the length of the piston rod in the hydraulic cylinder. Even if a long hydraulic cylinder is used, no adjacent saws may move closer together than the distance determined by the substantial width of the saw box. This limits the length of log segments that can be cut. It also limits the length of logs that may be processed by the apparatus.
Other examples of travelling saws are disclosed in the prior art. U.S. Pat. No. 5,179,883 to Payr discloses a saw carriage supported on guide rails on a floor-mounted frame. A motor-driven rope pulley, supported by guide rollers attached to the frame, drives the saw carriage laterally. Another travelling saw is described in U.S. Pat. No. 4,330,019 to Murphy. In this system, each saw rests on a floor-mounted carriage fitted with wheels that ride on rails. A pinion, rotated by a motor mounted on the saw carriage, extends out of the bottom of each saw carriage. The pinion meshes with a rack secured to one rail to move the saw carriage along the length of the apparatus. A similar travelling saw system is disclosed in U.S. Pat. No. 6,279,441 to Streblow.
In the case of each of the prior art systems described above, the saws are mounted on relatively bulky apparatus mounted on the floor adjacent the log delivery system. This makes it difficult or dangerous for personnel to move about the merchandiser, for example to clean or maintain it. In addition, the rail mounted saw assemblies that characterize the prior art require powerful drives to move the significant weight of the assemblies. This limits the accuracy and speed at which merchandising can take place.
There is therefore an advantage to moving the travelling saw assemblies in a log processing system off the floor, to a point above the log delivery system. One example of an overhead saw assembly is U.S. Pat. No. 5,142,955 to Hale, which discloses a travelling trim saw carried on an aluminum and low-friction plastic carriage slidably supported on an overhead box beam. Hale's carriage travels laterally approximately two feet under the control of a servomotor, which connects to a toothed pulley engaged with an endless belt supported by another toothed pulley. Another overhead saw system is described in U.S. Pat. No. 4,262,572 to Flodin, wherein the saw carriage, containing one main saw and two horizontal saws, is supported on guide wheels that run along an overhead track. U.S. Pat. No. 4,960,023 to Reuter discloses a third overhead saw system, wherein two sliding saw carriages, each containing a plurality of saws, are suspended on an overhead guide support. Upper and lower guide rolls, or other sliding guide elements, are used to support the saw carriages as they move along the guide support. The saw carriages are positioned with hydraulic cylinders fastened to the guide support stand.
These overhead travelling saw systems move parts of the log processing apparatus off the floor. However, the systems do not allow for a plurality of independently movable saws. In addition, the beams supporting the saws often restrict how far the saws may move in the lateral direction. Therefore, the length of logs that can be processed and the length of the cut logs are limited. This limits the efficiency of the log processing system.
It is an object of the present invention to increase the speed and efficiency of a log merchandiser. It is a further object of the present invention to reduce the complexity, weight and floor space required for the saw assembly and to provide a saw assembly that is highly accurate and versatile.
These and other objects of the invention will be appreciated by reference to the summary of the invention and to the detailed description of the preferred embodiment that follow.